“As the great megalopolis grows, we have more frequent and longer heat waves,” said Bill Patzert of NASA’s Jet Propulsion Laboratory.

Patzert points to the rapid growth of shopping centers, freeways, golf courses, and other local infrastructure are the main culprits behind the more intense heat we experience here in the Southland.

Land that was once dry and cooled down during the nighttime is now irrigated and functions as what Patzert called a “giant heat trap”, while tall buildings in our cities also can act as canyons that stifle any cooling waves.

“Temperatures on average are five degrees warmer than they were 50 years ago,” Patzert said. “That’s a lot!”

Those higher temperatures can linger well into the evening, making it seem as if the weather is barely cooling off overnight.